Technical Field
The present disclosure relates to a position indicator having a pen pressure detecting function, the position indicator being used in conjunction with a position detecting device, a pen pressure detecting module used in the position indicator, and a position indicator using the pen pressure detecting module.
Description of the Related Art
A position input device has recently been used as an input device for a tablet type PC (personal computer), a portable apparatus, or the like. This position input device includes, for example, a position indicator formed in the shape of a pen and a position detecting device having an input surface on which pointing operations and the input of characters, figures, and the like are performed by using the position indicator.
In related art, as a pen type of position indicator of this kind, a position indicator for an electromagnetic induction type of position detecting device is well known. The electromagnetic induction type position indicator has a resonance circuit formed by connecting a capacitor for resonance to a coil wound around a ferrite core. The position indicator indicates a position on the position detecting device by transmitting a resonance signal obtained in the resonance circuit to the position detecting device.
The pen type of position indicator of this kind in related art is also configured to have a function of detecting a pressure (pen pressure) applied to a tip portion (pen point) of a core body and transmitting the pressure (pen pressure) to the position detecting device. In this case, for detecting the pen pressure, a method is known which uses a mechanism that changes the inductance of the coil forming the resonance circuit according to the pen pressure, or a method is known which uses a mechanism that changes the capacitance of the capacitor forming the resonance circuit according to the pen pressure.
FIGS. 19A and 19B show an example of a constitution in related art of a pen pressure detecting mechanism part of a variable capacitance capacitor type that changes the capacitance of a capacitor forming a resonance circuit of a position indicator according to pen pressure. The example is described in Japanese Patent Laid-Open No. 2011-186803.
FIG. 19A is a general perspective view of the example of constitution of the pen pressure detecting mechanism part. FIG. 19B is a sectional view taken along a line A-A of FIG. 19A, and is a longitudinal sectional view of the pen pressure detecting mechanism part.
The pen pressure detecting mechanism part 100 in the example of FIGS. 19A and 19B uses, as a pressure sensing portion, a variable capacitance capacitor that changes capacitance based on a pressure (pen pressure) applied to a core body 101 (see alternate long and short dashed lines in FIG. 19B) of the position indicator. The position indicator detects the pen pressure applied to the core body 101 on the basis of the change in the capacitance of the variable capacitance capacitor, and transmits the detected pen pressure to a position detecting device.
As shown in FIG. 19A and FIG. 19B, the variable capacitance capacitor acting as the pressure sensing portion of the pen pressure detecting mechanism part 100 includes a dielectric 103, a terminal member 104, a retaining member 105, a conductive member 106, and an elastic member 107 within a cylindrical holder 102 formed of a resin, for example.
The dielectric 103, for example, has substantially a disk shape. The dielectric 103 has a first surface portion 103a and a second surface portion 103b, the second surface portion 103b being opposed to the first surface portion 103a so as to be substantially parallel to the first surface portion 103a. As shown in FIG. 19B, the dielectric 103 is mounted on a flange portion 102a of the holder 102 with the second surface portion 103b facing in an axial direction of the holder 102 toward an end of the holder 102 at which an end of the core body 101 is present.
The terminal member 104 is formed of a conductive metal. The terminal member 104 has a flat portion 104a engaged with the surface portion 103a of the dielectric 103, two locking portions 104b and 104c formed so as to be continuous from the flat portion 104a, and a lead piece 104d similarly formed so as to be continuous from the flat portion 104a. 
As shown in FIG. 19A and FIG. 19B, the opening portions 104e and 104f of the two locking portions 104b and 104c of the terminal member 104 are locked to locking pawl portions 102b and 102c of the holder 102, whereby the terminal member 104 is fixed to the holder 102.
The lead piece 104d of the terminal member 104 is connected to a contact portion of a printed board (not shown) disposed on an opposite side from the core body 101. The lead piece 104d of the terminal member 104 forms a first electrode of the variable capacitance capacitor.
The retaining member 105 has a base portion 105a having an outside diameter slightly smaller than the inside diameter of a hollow portion of the holder 102. An engaging recessed portion 105c (see FIG. 19B) recessed in substantially a cylindrical shape is provided in the base portion 105a. An end portion in the axial direction of the core body 101 is press-fitted into the engaging recessed portion 105c, whereby the core body 101 is coupled to the retaining member 105.
In addition, a fitting portion 105b for attaching the conductive member 106 is formed in the retaining member 105 so as to project to an opposite side from the core body 101 side of the base portion 105a. The conductive member 106 is fitted into the fitting portion 105b. 
The conductive member 106 is formed by an elastic member that is conductive and capable of elastic deformation. As shown in FIG. 19B, the conductive member 106 is formed in the form of a shell, for example, and has a curved surface portion 106a at one end in the axial direction of the conductive member 106. The diameter of the cylindrical portion 106b of the conductive member 106 is, for example, set somewhat larger than the inside diameter of the fitting portion 105b of the retaining member 105. The conductive member 106 is thereby fitted into the fitting portion 105b of the retaining member 105.
Because an elastic member is used as the conductive member 106, a contact area between the second surface portion 103b of the dielectric 103 and the curved surface portion 106a of the conductive member 106 is increased with an increase in pen pressure (pressure) applied to the core body 101.
The elastic member 107 is, for example, a conductive coil spring. The elastic member 107 has an elastic winding portion 107a, a terminal piece 107b at one end portion of the winding portion 107a, and a connecting portion 107c at another end portion of the winding portion 107a. As shown in FIG. 19B, the winding portion 107a of the elastic member 107 is disposed so as to cover the periphery of the conductive member 106 with the fitting portion 105b of the retaining member 105 interposed therebetween. The connecting portion 107c of the elastic member 107 comes into contact with the conductive member 106. The elastic member 107 is thereby electrically connected to the conductive member 106.
In addition, as shown in FIG. 19A, the terminal piece 107b of the elastic member 107 projects to one end in the axial direction of the holder 102 through a through hole (not shown) provided in the holder 102. The terminal piece 107b is connected to a contact portion (not shown) of the printed board. The terminal piece 107b of the elastic member 107 forms a second electrode of the variable capacitance capacitor.
Two engaging projecting portions 105d and 105e having a substantially triangular sectional shape are provided on two flat surface portions opposed to each other in side surface portions of the base portion 105a of the retaining member 105. The engaging projecting portions 105d and 105e are engaged with engaging holes 102d and 102e formed in the holder 102. In this engaged state, the elastic member 107 is retained between the flange portion 102a of the holder 102 and the base portion 105a, and the retaining member 105 is retained in the holder 102 in a state of being movable along the axial direction of the holder 102 by the length of the engaging holes 102d and 102e in the axial direction of the holder 102.
As shown in FIG. 19B, the curved surface portion 106a formed at one end in the axial direction of the conductive member 106 is disposed so as to be opposed to the second surface portion 103b of the dielectric 103, and the conductive member 106 forms the second electrode portion of the variable capacitance capacitor.
The variable capacitance capacitor acting as the pressure sensing portion of the pen pressure detecting mechanism part 100 formed as described above is shown in FIG. 19B in a state in which no pressure (pen pressure) is applied to the core body 101 (initial state). In the initial state, the conductive member 106 is physically separated from the second surface portion 103b of the dielectric 103, and is not in contact with the second surface portion 103b. When a pressure is applied to the core body 101, the thickness of an air layer between the conductive member 106 and the second surface portion 103b of the dielectric 103 becomes smaller than in the initial state.
Further, the pressure applied to the core body 101 may be increased, so that the curved surface portion 106a of the conductive member 106 comes into contact with the second surface portion 103b of the dielectric 103. The contact area between the second surface portion 103b of the dielectric 103 and the curved surface portion 106a of the conductive member 106 corresponds to the pressure applied to the core body 101.
The distance between the first electrode and the second electrode of the variable capacitance capacitor acting as the pressure sensing portion of the pen pressure detecting mechanism part 100 changes, as described above, according to the pressing force applied to the core body 101. Thus, the capacitance of a capacitor formed between the first electrode and the second electrode changes according to the pressing force applied to the core body 101.
As described above, the variable capacitance capacitor acting as the pressure sensing portion in the pen pressure detecting mechanism part of the variable capacitance capacitor type, which mechanism part has the constitution in related art has a large number of parts, such as the dielectric 103, the terminal member 104, the retaining member 105, the conductive member 106, the elastic member 107, and the like, and has a complex constitution. In addition, the first electrode of the variable capacitance capacitor needs to have a special structure in which an electric connection is secured by elastically crimping the first electrode to the surface of the dielectric 103. In addition, the second electrode of the variable capacitance capacitor needs to have a constitution in which the elastic member 107 is formed by a conductive coil spring, and the coil spring is electrically connected to the conductive member 106 that abuts against the dielectric and which changes an abutting area between the coil spring and the dielectric according to a pen pressure. This also results in a complex structure.
In addition, as described above, the pen pressure detecting mechanism part in related art has the constitution in which the plurality of mechanism parts as described above, which form the variable capacitance capacitor, are arranged in the axial direction of the core body of the position indicator within the hollow holder. There is thus a limit to the thinning of the pen pressure detecting mechanism part in related art. Electronic apparatuses including a position detecting device used in conjunction with a position indicator, for example, advanced portable telephone terminals referred to as smart phones, have been reduced in thickness. Thus, there has been a stronger desire to thin the position indicator. However, because there is a limit to the thinning of the constitution of the pen pressure detecting mechanism part in related art, it is difficult to further thin the position indicator.
In addition, the pen pressure detecting mechanism part in related art needs to be manufactured by inserting all of the plurality of parts of the pen pressure detecting mechanism part into the hollow portion of the cylindrical holder from both of one opening and another opening in the axial direction of the holder and arranging the parts within the hollow portion of the holder, and retaining the parts elastically in the axial direction.
Hence, the work of inserting all of the plurality of parts forming the pen pressure detecting mechanism part into the hollow portion of the holder and arranging the parts within the hollow portion of the holder while considering alignment of all of the plurality of parts in the axial direction and a direction orthogonal to the axial direction involves difficulty and increases the number of man-hours required for assembly. The pen pressure detecting mechanism part in related art is thus unsuitable for mass production.